As a high-performance permanent magnet, there have been known rare-earth magnets such as a Sm—Co based magnet and a Nd—Fe—B based magnet. When a permanent magnet is used for a motor of a hybrid electric vehicle (HEV) or an electric vehicle (EV), the permanent magnet is required to have heat resistance. In a motor for HEV or EV, a permanent magnet whose heat resistance is enhanced by dysprosium (Dy) substituting for part of neodymium (Nd) of the Nd—Fe—B based magnet is used. Since Dy is one of rare elements, there is a demand for a permanent magnet whose heat resistance is enhanced without using Dy. Further, in order to improve efficiency of a motor and a power generator, there is a demand for improvement in a coercive force and magnetic flux density of the permanent magnet.
It is known that, because the Sm—Co based magnet has a high Curie temperature, it exhibits excellent heat resistance without using Dy. The Sm—Co based magnet is drawing attention as a permanent magnet capable of realizing a good motor characteristic under high temperatures. A Sm2Co17 type magnet among the Sm—Co based magnets is expected as a permanent magnet used for a motor and a power generator because of its high coercive force and high magnetic flux density. However, it is becoming clear that, when a conventional Sm2Co17 type magnet is applied to a motor and a power generator, demagnetization is likely to occur in a surface portion of the magnet at the time of the operation under high temperatures. Therefore, there is a demand for a Sm2Co17 type magnet in which the high-temperature demagnetization in the surface portion is suppressed.